Salivary glands and oral lesions in diabetes mellitus an experimental and clinical study with special reference to the influence of metabolic control and duration of the disease
Abstract: Diabetes mellitus is associated with several clinically significant abnormalities in the oral cavity and salivary glands, the most common being periodontitis, salivary gland enlargement and a sensation of dry mouth. The prevalence of dental caries in diabetics is mostly reported to be decreased or unaffected. Since there is a shortage of information concerning the influence of metabolic control and duration of diabetes on these abnormalities, the present studies were performed.Three-month-old rats were made alloxan-diabetic and investigated after one and twelve months’ duration of diabetes for oral lesions and feeding behavior. They had free access to a standard pellet diet and tap water. Streptococcus mutans and lactobacilli were naturally occurring. In diabetic rats the proportion of the oral flora which was lactobacilli was positively correlated to the blood glucose level. Untreated long-term alloxan-diabetic rats developed advanced periodontal disease and root surface caries in the molars at sites of interdental impaction of foreign material. The degree of alveolar bone loss was positively correlated to the blood glucose level. Diabetic rats were hyperphagic and had a longer total eating time, including day-time eating, mainly by having longer meals but no significant increase of meal frequency, as compared with non-diabetic animals. The untreated alloxan-diabetic rats developed reduced salivary gland weight which was of the same degree in short- and longterm diabetic animals. Short- and long-term untreated alloxan-diabetic rats showed a similar degree of morpho- metrically estimated lipid accumulation in the acinar cells of the submandibular glands, and the degree was positively correlated to the blood glucose level. However, lipid inclusion occurred only in rats with a morning nonfasting blood glucose level exceeding 15 mmol/L. The capillaries in the submandibular glands of the untreated long-term alloxan-diabetic rats had a significantly increased thickness of the basement membranes as compared with the observations in short-term diabetic and non-diabetic rats. Untreated alloxan-diabetic rats were also shown to have a decreased salivary flow rate compared with non-diabetic rats, and the decreased flow was negatively correlated to the blood glucose concentration. Salivary flow rate increased with the duration of the disease. The diabetic rats had increased salivary glucose levels, which were positively correlated to blood glucose values when the latter were above 15 mmol/L, suggesting a threshold mechanism for salivary glucose excretion. Insulin therapy reversed salivary flow rate and salivary glucose concentrations toward normal.Salivary investigations were performed in eleven diabetic patients on two occasions with different metabolic control. Salivary flow rate showed marked interindividual differences but was not significantly changed by improved metabolic control although several of the patients initially had severely deranged glucose metabolism. A positive correlation between the glucose concentration in blood and saliva was seen in the parotid saliva during secretory stimulation. No significant change in electrolytes, amylase or antimicrobial factors was found.
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